Impact of Blending on Thermal Fingerprints of Waxes

Controlling the quality of raw materials is a needed step in ensuring the success of final products. In working with manufacturing processes, the crystallization and melting temperatures of natural products are influenced by the origin of raw materials. Using RheolaserCrystal, the aforementioned parameters could easily be verified, such that quality and any process adjustment are validated.

Reminder on the Technique

RheolaserCRYSTAL® utilizes the DWS principes that sends a laser beam onto the sample, allowing the scattered light to create an interference wave. The variatio in the pattern is related to the particles’ motion where a faster difference between 2 speckles yields higher scatterer mobility.

Micro-Dynamics (Hz) refers to the speed of variation between 2 images. Plotted against time and temperature, it presents a characteristic peak for microstructural evolution, such as a phase transition. High values imply either a fast scatterer motion currently taking place or an evolution of a structure.

The signal can then be integrated for an easier visualization, obtaining the so-called Micro Dynamics Evolution percentage.

Method

In this article, a thermal analyses of the following were carried  out:

  1. Four different waxes and oils;
  2. Three mixtures of two waxes prepared with different blending processes

Rheolaser Crystal - Formulaction - Thermal analysis on macroscopic samples from Formulaction on Vimeo.

Part 1: Pure Waxes and Oils

Three pure waxes (candelilla, carnauba, bee) were analyzed alongside palm oil. All samples were heated from 4 °C to 90 °C with a rate of 5 °C/ min. During heating, the four pure materials underwent a phase transition, from a solid crystalline state to a liquid phase. Such phenomenon corresponds to the increase of MicroDynamics Evolution (µDE) from 0% to 100%. This melting point is viewed as the average transition temperature, T50. Similarly, the temperatures corresponding to 10% and 90% of the total phase transition are T10 and T90, respectively.

Part 2: Mixed Waxes

Waxes and oils are typically blended into final products. This is done to produce a better texture and maintain good stability in terms of time and temperature. The phase transition temperature of the mixture is different in comparison to the pure compound.

The candelilla and bee waxes are mixed in a ratio of 1:1 and cooled in three different wats. They were mixed at temperature of 90 °C and then cooled down to 4 °C respectively at the following speeds:

  1. 2 °C/min; inside the instrument
  2. 25 °C/min; inside the instrument
  3. Cooled directly in an ice bath

After the mixtures have been cooled, they are then reheated using the same protocol as in Part 1, at 5 °C/min from 4 °C to 90 °C. This is facilitated in order to study the melting process.

Results

Part 1: Pure Waxes and Oils

The values, including the difference between T10 and T90 (∆T), are presented in the table below. A small value of ∆T implies good uniformity of the microstructure. An example is palm oil. In this product, the increase of signal at temperatures as low as 20 °C—the melting point of some lipids—showed its poor heat stability.

Micro-Dynamics Evolution as a function of temperature for three pure waxes and an oil (Palm Oil, Bee wax, Candelilla, Carnauba)

Figure 1. Micro-Dynamics Evolution as a function of temperature for three pure waxes and an oil (Palm Oil, Bee wax, Candelilla, Carnauba)

Transition temperatures during the heating of three pure waxes and an oil

Table 1. Transition temperatures during the heating of three pure waxes and an oil

Part 2: Mixed Waxes

The figure below presents the Micro-Dynamics Evolution of the pure bee wax, the pure candelilla wax, and their three mixtures (A, B, C). It was found that the heating curves for the three mixtures were between those of two pure waxes.

μDE (%) as a function of temperature Bee wax, Candelilla and the three mixtures A, B, C.

Figure 2. μDE (%) as a function of temperature Bee wax, Candelilla and the three mixtures A, B, C.

The characteristic temperature values are presented in the below table. The T50 increased and the ∆T decreased as a result of accelerating the recrystallization process during blending. In this case, a rapid crystallization results in a creation of a eutectic crystalline structure that has a thermal signal similar to a pure candelilla wax.

Transition temperatures for Bee wax, Candelilla and the three mixtures A, B, C.

Table 2. Transition temperatures for Bee wax, Candelilla and the three mixtures A, B, C.

Conclusion

The RheolaserCRYSTAL® could accurately differentiate the various melting and crystallization temperatures of raw materials such as oils and waxes. Through this method, operators are able to work with macroscopic samples, thereby preventing any issue of denaturenation during sampling. This method also facilitates the analysis of heterogenous products. The precise temperature control (0.10°C/min to 25°C/min for heating or cooling) allows manufacturers to easily control raw materials, optimize mixing processes, and ensure a better quality of final products.

This information has been sourced, reviewed and adapted from materials provided by Formulaction.

For more information on this source, please visit Formulaction.

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